Walsh & Hoyt: Contrast Sensitivity

Visual acuity defines the smallest spatial detail that can be resolved for high-contrast stimuli, but it does not specify the responses of the visual system to objects of different sizes and contrasts. Measurement of the spatial contrast sensitivity function (CSF) is necessary to obtain this information. The CSF is most commonly determined by measuring contrast thresholds for sinusoidal gratings, an alternating pattern of light and dark bars with luminance that varies sinusoidally in a direction perpendicular to orientation of the grating. The size of the grating is specified according to spatial frequency, which is the number of cycles (pairs of light and dark bars) of the grating pattern per degree of visual angle. Typically, between 3 and 10 spatial frequencies from 0.5 to 30 cycles per degree are measured for the CSF.